Semiconductor assemblies and structures

ABSTRACT

Semiconductor assemblies, structures, and methods of fabrication are disclosed. A coating is formed on an electrically conductive pillar. The coating, which may be formed from at least one of a silane material and an organic solderability protectant material, may bond to a conductive material of the electrically conductive pillar and, optionally, to other metallic materials of the electrically conductive pillar. The coating may also bond to substrate passivation material, if present, or to otherwise-exposed surfaces of a substrate and a bond pad. The coating may be selectively formed on the conductive material. Material may not be removed from the coating after formation thereof and before reflow of the solder for die attach. The coating may isolate at least the conductive material from solder, inhibiting solder wicking or slumping along the conductive material and may enhance adhesion between the resulting bonded conductive element and an underfill material.

TECHNICAL FIELD

The present disclosure, in various embodiments, relates generally tosemiconductor structures, such as semiconductor die assemblies, and tomethods of fabrication of the assemblies and structures.

BACKGROUND

Processed semiconductor dice containing integrated circuits may beelectrically and physically connected with other semiconductor dice,semiconductor dice in wafer or partial wafer form, interposers, circuitboards, and other higher-level packaging, any such structureshereinafter collectively referred to as “substrates,” to operablyconnect the integrated circuits on the semiconductor die with those onanother substrate. This connection may use a large number ofelectrically conductive elements protruding from a major surface, suchas the active surface or a backside surface, of the semiconductor die orsemiconductor dice in wafer or partial wafer form. The conductiveelements may comprise an electrically conductive bump, stud, column, orpillar, which may in some instances be in the form of a cylindricalstructure. The conductive element may reside on a conductive pad,referred to in the art as a “bond pad,” on an active surface of thesemiconductor substrate.

To accomplish the electrical and physical interconnection, thesemiconductor die, which may be included in a wafer or partial waferform, may be inverted, i.e., flipped upside down, and bonded to anotherconductive material, referred to in the art as a “landing pad,” onanother substrate. Bonding, which may be effected using a soldermaterial that is melted and then solidified, is accomplished during aprocessing stage known as “die attach.” Thus, during die attach, thesemiconductor die, which may be referred to in the art as “die one,” iselectrically and physically interconnected with the substrate, which, ifthe substrate comprises the base semiconductor die of a stacked dieassembly, may be referred to as “die zero.” Multiple such dice may bestacked upon one another in this manner to form a stacked semiconductordie assembly. If the semiconductor die was in a wafer form during dieattach, the wafer may be singulated to form individual or groups ofprocessed semiconductor dice.

As noted above, a solder material may be used to accomplish the dieattach. The solder material may be in the form of solder mass, alsoknown in the art as a “solder ball” or a “solder bump,” supported byanother material of the conductive element or directly by a bond pad.During die attach, the solder may be reflowed in proximity with theconductive element and the landing pad, optionally in the presence of aflux material.

Before or during reflow of the solder, during die attach, during diestacking, during subsequent processing, or any combination thereof, thesolder may slump, or even wick, along the periphery of a supportingmaterial of the electrically conductive element. Either or both ofsolder slumping or wicking may lead to undesirable formation ofintermetallic materials due to reaction between one or more materialswithin the solder and one or more materials within the supportingmaterial of the conductive element. For example, conventional conductiveelements may include a conductive material, e.g., copper, which mayreact and form an intermetallic material with a material of aconventional solder material used for die attach, e.g., tin, disposedover the conductive material, for example, at an end of the conductiveelement. Growth of such a copper-tin intermetallic material may proceedat a significant pace, leading to deterioration of the conductive pillarand potential formation of Kirkendall voids within the conductiveelement. The formation of the intermetallic material can cause problemsduring temperature cycling testing and high-temperature storage testingas well as during operation of the semiconductor dice employing theconductive elements.

Solder wicking or slumping can also leave an insufficient volume ofsolder disposed between the conductive element and the landing pad,weakening the strength of the bond. Substantial solder wicking orslumping can lead to failure of the joint between the conductive elementand landing pad.

Conventional conductive elements may include a conductive barriermaterial disposed between the conductive material of the conductiveelement and the region of the conductive element in contact with thesolder material during solder reflow and die attach. The barriermaterial may, at least initially, prevent direct contact between theconductive material and the solder. However, the presence of the barriermaterial does not necessarily inhibit the solder from slumping orwicking along the sides of the electrically conductive element andundesirably coming into contact with the conductive material of theconductive element. Therefore, use of a barrier material on theconductive element may not, by itself, sufficiently inhibit solderwicking and slumping, formation of intermetallic materials, bondweakness, or joint failure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1D are cross-sectional elevation views of asemiconductor structure of a pillar-on-passivation configuration duringvarious stages of a bonding method according to an embodiment of thepresent disclosure.

FIGS. 2A through 2D are cross-sectional elevation views of asemiconductor structure of a pillar-on-pad configuration during variousstages of a bonding method according to an embodiment of the presentdisclosure.

FIGS. 3A through 3D are cross-sectional elevation views of asemiconductor structure of a pillar-on-passivation configuration duringvarious stages of a bonding method according to an embodiment of thepresent disclosure.

FIGS. 4A through 4D are cross-sectional elevation views of asemiconductor structure of a pillar-on-pad configuration during variousstages of a bonding method according to an embodiment of the presentdisclosure.

FIGS. 5A through 5D are cross-sectional elevation views of asemiconductor structure of a pillar-on-passivation configuration duringvarious stages of a bonding method according to an embodiment of thepresent disclosure.

FIG. 6 is a cross-sectional elevation view of a stacked semiconductordie assembly formed according to the bonding method of FIGS. 1A through1D.

FIG. 7 is a cross-sectional elevation view of a stacked semiconductordie assembly formed according to the bonding method of FIGS. 2A through2D.

FIG. 8 is a cross-sectional elevation view of a stacked semiconductordie assembly formed according to the bonding method of FIGS. 3A through3D.

FIG. 9 is a cross-sectional elevation view of a stacked semiconductordie assembly formed according to the bonding method of FIGS. 4A through4D.

FIG. 10 is a cross-sectional elevation view of a stacked semiconductordie assembly formed according to the bonding method of FIGS. 5A through5D.

DETAILED DESCRIPTION

Methods of forming semiconductor die assemblies and semiconductorstructures are disclosed. Semiconductor die assemblies and semiconductorstructures are also disclosed. The devices and assemblies includeconductive elements having a coating thereon. More specifically, theconductive elements include an electrically conductive material on whichthe coating is formed. The coating may, optionally, be formed over othermaterials disposed on the conductive element. The coating isolates theconductive material from a solder material used to bond the conductiveelement to inhibit the solder from wicking, or slumping, and coming intocontact with the conductive material.

A precursor composition used to form the coating, which composition isreferred to herein as the “coat-forming composition,” may be formulatedto cover the otherwise-exposed surfaces of the conductive element, whichmay be configured as a pillar, including the conductive material, aswell as other otherwise-exposed surfaces of the conductive element. Sucha coat-forming composition may include, for example, a silane material.Alternatively, the coating may be formed from a material that isselective for the conductive material of the conductive element so as toform the coating essentially only on otherwise-exposed surfaces of theconductive material of the conductive element.

After formation of the coating and, in some embodiments, without firstremoving material from the coating, solder may be reflowed in proximityto the conductive material of the conductive element to electrically andphysically connect the conductive element with another conductivematerial, such as a landing pad of a substrate. The coating maypassivate the conductive material, isolating it from a solder materialused during die attach. The coating inhibits the solder material fromcoming into contact with the coated materials, e.g., the conductivematerial, such that the solder is inhibited from wicking or slumpingalong at least the conductive material of the electrically conductivepillar. Therefore, the likelihood of die collapse, intermetallicformation, and joint failure is decreased relative to the likelihood ofsuch events occurring with bond joints employing conventional,non-passivated conductive elements. The coating may also inhibitcorrosion of the coated components and may improve adhesion between thecoated structures and an underfill material disposed between adjacentcomponents of the resulting assembly, contributing to the environmentaland mechanical stability of the assembly.

As used herein, the term “semiconductor substrate” means and includes abase material or construction upon which components, such as those ofmemory cells and peripheral circuitry, as well as logic, are formed. Thesemiconductor substrate may be a substrate wholly of a semiconductormaterial, a base semiconductor material on a supporting structure, or asemiconductor substrate having one or more materials, structures, orregions formed thereon. The semiconductor substrate may be aconventional silicon substrate or other bulk substrate including asemiconductive material. As used herein, the term “bulk substrate” meansand includes not only silicon wafers, but also silicon-on-insulator(“SOI”) substrates, such as silicon-on-sapphire (“SOS”) substrates orsilicon-on-glass (“SOG”) substrates, epitaxial layers of silicon on abase semiconductor foundation, or other semiconductor or optoelectronicmaterials, such as silicon-germanium (Si_(1-x)Ge_(x), where x is, forexample, a mole fraction between 0.2 and 0.8), germanium (Ge), galliumarsenide (GaAs), gallium nitride (GaN), or indium phosphide (InP), amongothers. Furthermore, when reference is made to a “semiconductorsubstrate” in the following description, previous process stages mayhave been utilized to form materials, regions, or junctions, as well asconnective elements such as lines, plugs, and contacts, in the basesemiconductor structure or foundation, such components comprising, incombination, integrated circuitry.

As used herein, spatially relative terms, such as “beneath,” “below,”“lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,”“right,” and the like, may be used for ease of description to describeone element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. Unless otherwise specified,the spatially relative terms are intended to encompass differentorientations of the materials in addition to the orientation depicted inthe figures. For example, if materials in the figures are inverted,elements described as “below” or “beneath” or “under” or “on bottom of”other elements or features would then be oriented “above” or “on top of”the other elements or features. Thus, the term “below” can encompassboth an orientation of above and below, depending on the context inwhich the term is used, which will be evident to one of ordinary skillin the art. The materials may be otherwise oriented (rotated 90 degrees,inverted, flipped, etc.) and the spatially relative descriptors usedherein interpreted accordingly.

As used herein, reference to an element as being “on” or “over” anotherelement means and includes the element being directly on top of,adjacent to, underneath, or in direct contact with the other element. Italso includes the element being indirectly on top of, adjacent to,underneath, or near the other element, with other elements presenttherebetween. In contrast, when an element is referred to as being“directly on” another element, there are no intervening elementspresent.

As used herein, the terms “comprises,” “comprising,” “includes,” and/or“including” specify the presence of stated features, regions, integers,stages, operations, elements, materials, components, and/or groups, butdo not preclude the presence or addition of one or more other features,regions, integers, stages, operations, elements, materials, components,and/or groups thereof.

As used herein, “and/or” includes any and all combinations of one ormore of the associated listed items.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

Embodiments are described herein with reference to the illustrations.The illustrations presented herein are not meant to be actual views ofany particular material, component, structure, device, or system, butare merely idealized representations that are employed to describeembodiments of the present disclosure. Variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, embodiments describedherein are not to be construed as being limited to the particular shapesor regions as illustrated, but include deviations in shapes that result,for example, from manufacturing. For example, a region illustrated ordescribed as box-shaped may have rough and/or nonlinear features, and aregion illustrated or described as round may include some rough and/orlinear features. Moreover, sharp angles that are illustrated may berounded, and vice versa. Thus, the regions illustrated in the figuresare schematic in nature, and their shapes are not intended to illustratethe precise shape of a region and do not limit the scope of the presentclaims.

The following description provides specific details, such as materialtypes and processing conditions, in order to provide a thoroughdescription of embodiments of the disclosed devices and methods.However, a person of ordinary skill in the art will understand that theembodiments of the devices and methods may be practiced withoutemploying these specific details. Indeed, the embodiments of the devicesand methods may be practiced in conjunction with conventionalsemiconductor fabrication techniques employed in the industry.

The fabrication processes described herein do not form a completeprocess flow for processing semiconductor structures. Preceding,intermediary, and final process stages are known to those of ordinaryskill in the art. Accordingly, only the methods and semiconductorstructures necessary to understand embodiments of the present devicesand methods are described herein.

Unless the context indicates otherwise, the materials described hereinmay be formed by any conventional technique including, but not limitedto, dip coating, spin coating, spray coating, blanket coating, chemicalvapor deposition (“CVD”), plasma enhanced CVD, atomic layer deposition(“ALD”), plasma enhanced ALD, or physical vapor deposition (“PVD”).Alternatively, the materials may be grown in situ, unless the contextotherwise indicates. Depending on the specific material to be formed,the technique for applying, depositing, growing, or otherwise formingthe material may be selected by a person of ordinary skill in the art.

Reference will now be made to the drawings, where like numerals refer tolike components throughout. The drawings are not necessarily to scale.

While various embodiments of the disclosure are described in detail withreference to a single conductive element and passivation and subsequentbonding thereof to another conductive structure, such description ismerely for clarity and convenience, as in practice a large number, whichmay reach tens of thousands, of such conductive elements are present ona bulk semiconductor substrate such as a semiconductor wafer, includinghundreds if not thousands of unsingulated semiconductor dice thereon.Each semiconductor die, in turn, has a number of conductive elementsformed on and protruding from a major surface, such as an activesurface, of the semiconductor substrate.

FIG. 1A illustrates a conductive element 100 employed in a configurationreferred to herein as a “pillar-on-passivation” configuration. Theconductive element 100 includes an electrically conductive pillar 110that includes a conductive material 112 and a barrier material 114. Theconductive material 112 may include copper. For example, withoutlimitation, the conductive material 112 may consist essentially ofcopper. The conductive material 112 may, for example, have a thickness(e.g., height) between about 1 micron and about 25 microns, e.g., 15microns. The barrier material 114 may include nickel. For example,without limitation, the barrier material 114 may consist essentially ofnickel. The barrier material 114 may, for example, have a thicknessbetween about 1 micron and about 25 microns, e.g., 3 microns.

The electrically conductive pillar 110 may be supported by a bond pad124. The bond pad 124 is, optionally, in operable communication withanother electrically conductive element, such as electrically conductivevia 122, which may be in operable communication with integratedcircuitry formed on or in semiconductor substrate 120, from which theelectrically conductive pillar 110 extends, in operable communicationwith the electrically conductive via 122 extending through semiconductorsubstrate 120 to an opposing side thereof, or both. Bond pad 124 may bein direct communication with integrated circuitry of semiconductorsubstrate 120, and, in some embodiments, the electrically conductive via122 may not be present.

According to the pillar-on-passivation configuration illustrated, asubstrate passivation material 126, such as a polyimide material, may beformed over the bond pad 124 and the semiconductor substrate 120.Openings may be defined in the substrate passivation material 126 toallow physical contact between the conductive material 112 of theelectrically conductive pillar 110 and the bond pad 124. In such aconfiguration, the electrically conductive pillar 110 is in contact withonly a portion of the bond pad 124 and the substrate passivationmaterial 126 covers otherwise-exposed surfaces of the bond pad 124 andthe substrate 120.

A mass of solder 130 may be supported by the electrically conductivepillar 110 and may be separated from the conductive material 112 by thebarrier material 114. The solder 130 may be a eutectic composition oftin and silver, e.g., a tin-silver solder material, and may have athickness (e.g., height) of about 15 microns before reflow.

The solder 130 may, optionally, be reflowed, prior to die attach, forexample, by heating the solder 130 above its melting point, optionallyin the presence of flux. Treating the solder 130 with flux may enhancereflow of the solder 130, e.g., by discouraging oxidation of the solder130 during reflow, by acting as a wetting agent, and by reducing surfacetension of reflowed (i.e., melted) solder 130 to increase itsflowability. The pre-die-attach reflow may provide a mass of solder 130of a rounded shape, as illustrated in FIG. 1A.

With reference to FIG. 1B, following formation of the conductive element100 (FIG. 1A), a coating 170 may be formed on at least one of thematerials of the conductive element 100. The coating 170 may be formedafter the optional initial reflow of the solder 130 with or withoutflux, if such initial reflow is performed.

The coating 170 may be formed on the conductive element 100 by exposingthe conductive element 100 to a coat-forming composition. One or morematerials of the coat-forming composition, e.g., the coating material,may be reactive with one or more materials of the conductive element100. The term “coating composition,” as used herein, refers to thecomposition of the resulting, formed coating 170. The coat-formingcomposition may not necessarily be identical to the coating compositiondue to, e.g., chemical reaction between the coat-forming composition andthe material of the conductive element 100 during formation of thecoating 170.

The coat-forming composition may be formulated to form a coating on theother-wise exposed surfaces of some or all of the materials of theconductive element 100, e.g., on essentially all otherwise-exposedsurfaces of the conductive element 100.

The coat-forming composition may include, for example and withoutlimitation, a silane material. As used herein, the terms “silane” and“silane material” mean and include a chemical compound including siliconand at least one other element, e.g., carbon, hydrogen, nitrogen,sulfur, or a combination thereof. Silane materials may be formulated asnon-functional silanes or as functional silanes.

As used herein, the term “non-functional silane” means a silane materialreactive with metallic material of the conductive element but lacking afunctional group reactive with a nonmetallic material of the conductiveelement. Examples of non-functional silane materials include, but arenot limited to, silane compounds including the formula —Si—(OC₂H₅)_(x),where x is an integer, and including either a methoxy or an ethoxygroup. The methoxy or ethoxy group is hydrolyzable to form a silanol(i.e., a Si—OH bond), with an alcohol (e.g., methanol or ethanol) formedas a by-product.

As used herein, the term “functional silane” means a silane materialreactive with metallic material of the conductive element and having afunctional group reactive with a nonmetallic material of the conductiveelement. Examples of functional silanes include, but are not limited to,silane coupling agents. As used herein, the term “silane coupling agent”means and includes a hybrid organic-inorganic compound with the formula(XO)₃Si(CH₂)_(q)Y, where XO represents a hydrolyzable alkoxy group(e.g., methoxy, ethoxy), q represents an integer, and Y represents afunctional group, such as, for example and without limitation, an amino,sulfur, carboxyl, or thiol group. For example, without limitation, afunctional silane material according to embodiments of the presentdisclosure may be an organofunctional silane with one or more of theorganofunctional groups or chemical structures in Table 1, which tableis not exhaustive.

TABLE 1 Example Organofunctional Groups and Example Chemical StructuresOrganofunctional Group Example Chemical Structure Vinyl H₂C═CHSi(OCH₃)₃Chloropropyl Cl(CH₂)₃Si(OCH₃)₃ Epoxy

Methacrylate

Primary amine H₂N(CH₂)₃Si(OCH₃)₃ Diamine H₂N(CH₂)₂NH(CH₂)₃Si(OCH₃)₃Mercapto HS(CH₂)₃Si(OCH₃)₃

When a silane material, either functional or non-functional, ishydrolyzed in water, or, alternatively, in an alcohol and water mixture,silanol groups (i.e., Si—OH groups) may form. The silanol groups of thehydrolyzed coat-forming composition may be reactive with hydroxyl groupson the surface of a metal that has been exposed to oxygen and moisture.That is, exposure of a metal structure to oxygen may form metal oxideson the surface of the metal structure. Subsequent exposure of the formedmetal oxides to moisture may form M-OH bonds, where M represents a metal(for example, and without limitation, Cu, Ni, Sn, Al, Ag). Thus, metalcomponents of the conductive element 100 may include hydroxyl bonds ontheir surfaces. Exposure of such hydroxyl bonds to silanol groups of ahydrolyzed silane material may lead to reaction, e.g., a condensationreaction, of the hydroxyl groups with the silanol groups, forming M-O—Sibonds, where M represents a metal. Accordingly, exposure of a metalliccomponent of the conductive element 100 to a coat-forming compositionincluding a silane material, water, and, optionally, an alcohol, mayaccommodate reaction between the coat-forming composition and thesurface of the metallic composition to form a coating on the metalliccomponent where the coating has a coating composition including M-O—Sibonds, also referred to herein as “metal-oxygen-silicon bonds.”

Both functional and non-functional silane materials may be formulated toreact with metallic components, as described above. Examples of such anon-functional silane include, without limitation, abis-[triethoxysilyl]ethane (BTSE) and a tetraethyl orthosilicate (TEOS)of the formula Si—(OC₂H₅)₄.

Functional silane materials may be formulated to be additionallyreactive. For example, in embodiments in which the silane material ofthe coat-forming composition includes an alkoxy (e.g., methoxy, ethoxy)group, the alkoxy groups are hydrolyzable to form silanols that mayreact with the hydroxyl groups of metallic components of the conductiveelement 100. The hydroxyl groups of the metallic components may havebeen formed on the metallic components as described above. For example,without limitation, the alkoxy (e.g., methoxy, ethoxy) groups of thesilane material in the coat-forming composition may be hydrolyzed tosilanols as illustrated in the following example reactions:R′Si(OR)₃+H₂O

R′Si(OR)₂OH+ROHR′Si(OR)₂OH+H₂O

R′Si(OR)(OH)₂+ROHR′Si(OR)(OH)₂+H₂O

R′Si(OH)₃+ROHwherein R′ and R represent hydrocarbons. The silanols may then reactwith metal hydroxides to form the M-O—Si bonds (metal-oxygen-siliconbonds) and water as illustrated in the following example reaction,wherein the dashed boundary illustrates a surface of a metal material ofthe conductive element 100:

Examples of such alkoxy-including functional silane materials include,for example and without limitation, mono silanes such asy-aminopropyltriethyoxysilanes (y-APS),y-methacryloxypropyltriethoxysilanes (y-MPS), andy-glycidoxypropyltrimethoxysilanes (y-GPS), and bis silanes such asbis-[trimethoxysilylpropyl]amine (available under the name SILQUEST®A-1170 Silane from Crompton OSi Specialties),bis[3-triethoxysilylpropyl]tetrasulfide (available under the nameSILQUEST® A-1289 Silane from Crompton OSi Specialties).

The silane material of the coat-forming composition may alternatively oradditionally be formulated to include other functional groups. Forexample, and without limitation, a functional silane material includingsulfur functional groups may react with metal within metalliccomponents, forming M-S bonds, also referred to herein as “metal-sulfurbonds.” For example, a sulfur group of a sulfur-based functional silanematerial may react with copper within a metallic component to form Cu—Sbonds, i.e., “copper-sulfur bonds.” Therefore, such formed coating 170may have a coating composition including M-S bonds.

Silanol groups of a silane material, whether functional ornon-functional, may also condense with one another during formation ofthe coating 170, forming Si—O—Si bonds, i.e., “silicon-oxygen-siliconbonds.” The formation of the Si—O—Si bonds may increase the density andthe viscosity of the coating material as the coating 170 forms.Therefore, the formed coating 170 may have a coating compositionincluding Si—O—Si bonds.

Functional silanes may be formulated to also react with nonmetallicmaterials of the conductive element 100. For example, a functionalsilane material of a coating material may be formulated so that one ormore functional groups within the functional silane material react withone or more functional groups within the substrate passivation material126, e.g., a group within a polyimide-based substrate passivationmaterial. The functional silane material may additionally oralternatively be formulated to react with a material within thesubstrate 120, within other nonmetallic components (not shown) of theconductive element 100, or within both if such materials are exposed tothe coating material within the coat-forming composition duringformation of the coating 170.

Accordingly, a coat-forming composition may be formulated (e.g., toinclude a non-functional silane material) so as to react with and form abonded coating on only metallic materials of the conductive element 100(e.g., the solder 130, the barrier material 114, and the conductivematerial 112). Alternatively, as illustrated in FIG. 1B, thecoat-forming composition may be formulated (e.g., to include afunctional silane material) so as to react with and form a bondedcoating 170 on the metallic components of the conductive element 100(e.g., the solder 130, the barrier material 114, and the conductivematerial 112) as well as on the nonmetallic components of the conductiveelement 100 (e.g., the substrate passivation material 126 and materialof the semiconductor substrate 120, if regions of the semiconductorsubstrate 120 are otherwise exposed).

Because the coat-forming composition may be formulated to cover, reactwith, and form a bonded coating 170 on the outer surfaces of essentiallyall exposed materials of the conductive element 100 and semiconductorsubstrate 120, the coating 170 may form on and cover essentially allotherwise-exposed surfaces of the conductive element 100, i.e., theotherwise-exposed surfaces of the electrically conductive pillar 110,including the conductive material 112 and the barrier material 114, aswell as the otherwise-exposed surfaces of the solder 130 and thesubstrate passivation material 126. Thus, the coating 170 may be asubstantially continuous, substantially conformal coating in directcontact with the conductive material 112, the barrier material 114, thesolder 130, and the substrate passivation material 126.

In other embodiments, the coat-forming composition may be formulated tocover some, but not all, of the otherwise-exposed surfaces of the solder130 and the conductive material 112, or formulated to cover one of thesolder 130 and the conductive material 112, but not both. In still otherembodiments, select surfaces of the conductive element 100 may beexposed to the coat-forming composition to selectively form anon-continuous coating over one or more surfaces of the materials of theconductive element 100. In any regard, the coating 170 isolates thesolder 130 from the conductive material 112.

In still other embodiments, a coating may be formed on only the solder130 of the electrically conductive pillar 110. As such, the solder 130,when reflowed, may be inhibited from wicking or slumping along theconductive material 112.

In further other embodiments, a coating may be formed on conductivematerials of the electrically conductive pillar 110 except the solder130. That is, the coating, in such further embodiments, may be formed onthe conductive material 112 and the barrier material 114 and not on thesolder 130. Though the coating may not be formed on the solder 130, thecoating on the conductive material 112 and the barrier material 114nonetheless inhibits contact between the solder 130, e.g., after reflow,and the conductive material 112.

The coating 170 may be formed by exposing surfaces of one or morematerials of the conductive element 100 desired to be covered to thecoat-forming composition. The surfaces of the conductive element 100 maybe exposed to the coat-forming composition within a coating solution,and the conductive element 100 may be dip coated, spin coated, spraycoated, or otherwise covered with the coating solution.

Such a coating solution may include the coat-forming composition, asolvent, and, optionally, water. The solvent used in the coatingsolution may be a water-based solvent, i.e., a solvent miscible inwater, or an organic solvent. For example, an organic solvent such as analcohol (e.g., methanol, ethanol), in which the coat-forming compositionis miscible, may be used to form the coating solution to be used to formthe coating 170.

The solvent used in the coating solution may be selected such that thecoating solution is formulated to discourage gelling of the coat-formingcomposition within the coating solution. As used herein, the term“gelling” means and includes thickening of the coating solution,increasing viscosity of the coating solution, and decreasing flowabilityof the coating solution prior to exposure of the conductive element 100to the coating solution. For example, use of an alcohol (e.g., methanol,ethanol) as the solvent in a silane-including coating solution maydiscourage gelling of the silane material, accommodating flowability ofthe coating solution during application thereof on the conductiveelement 100.

In embodiments in which the coat-forming composition includes a silanematerial, the coat-forming composition further includes water, e.g.,deionized water, to facilitate hydrolysis of the silane material to formthe aforementioned reactive silanols. The presence of water within thecoating solution may also facilitate formation of metal oxide and metalhydroxyl groups on the metallic materials of the conductive element 100when the conductive element 100 is exposed to the coating solution. Inother embodiments, the coating solution may be formed, initially, e.g.,with the coat-forming composition in the solvent, in the absence ofwater, and the water may be introduced to the coating solution beforethe solution, e.g., the coat-forming composition and the solvent, areapplied to the surfaces of the conductive element 100. In still otherembodiments, the surfaces of the conductive element 100 may be firstexposed to water and then exposed to the other components (e.g.,coat-forming composition and solvent) of the coating solution.

The coating solution may be formed by adding the coat-formingcomposition (e.g., silane material) to the solvent (e.g., alcohol), andthen adding water (e.g., deionized water). During and following additionof the chemicals to the coating solution, the solution may be stirred toinhibit gelling of the silane material.

The coating solution may be formulated to exhibit a pH in the range ofabout 4 to about 9 prior to application of the coating solution on theconductive element 100, which pH range may discourage gelling of thecoat-forming composition (e.g., silane material). A coating solutionwith a pH lower than about 2 or about 3 or a pH greater than about 10,on the other hand, may facilitate gelling of the silane material beforeexposure of the conductive element 100 to the coating solution.

The coating solution may include from about 1% by volume to about 5% byvolume coat-forming composition (e.g., silane material), based on thetotal volume of the coating solution. For example, without limitation,the coating solution may include about 5% by volume coat-formingcomposition (e.g., silane material), about 90% by volume ethanol orother alcohol-based solvent, and about 5% by volume deionized water.

In some embodiments, such as that illustrated in FIGS. 1B through 1D,the coating 170 may have an essentially uniform thickness over thematerials of the conductive element 100. In other embodiments (notshown), the coating 170 may be thicker in some areas, but relativelyuniform over the majority of the conductive material 112. As usedherein, “relatively uniform,” in referring to thickness, means athickness varying in height less than about 10% from one area of thecoating to another area of the coating. In some embodiments, the coating170 may have an average thickness of from about 50 nanometers to about500 nanometers.

The average thickness of the coating 170 may be dependent upon theconcentration of the coating material in the coating solution used toform the coating 170. For example, a coating solution with a higherconcentration of silane material, relative to a solvent and, if present,other components of the coating solution, may result in a thickercoating 170 compared to a coating solution with a lower concentration ofsilane material. However, coating solutions of high concentrations ofsilane material may have a higher propensity to gel than those withlower concentrations of silane material. Therefore, the concentration ofthe coat-forming composition in the coating solution used to form thecoating 170 may be tailored to achieve a coating 170 of a desiredaverage thickness without excessive gelling. For example, and withoutlimitation, a coating solution including about 5% by volume coat-formingcomposition (e.g., silane material), about 90% by volume ethanol orother alcohol-based solvent, and about 5% by volume deionized water maybe tailored to produce a coating 170 with a thickness, averaged over allthe coated components of the conductive element 100 or, alternatively oradditionally, averaged over only the conductive material 112, of about250 nanometers to about 500 nanometers. As another example, withoutlimitation, a coating solution including about 2% by volume coatingmaterial (e.g., silane material) may be formulated to produce a coating170 with an average thickness of about 80 nanometers to about 200nanometers.

Application of such a coating solution may be self-limiting such thatone application of the coating solution covers the exposed surfaces ofthe conductive element 100 to saturation. However, in some embodiments,multiple applications of the coating solution may be conducted to ensureformation of a continuous coating 170. Exposure of the conductiveelement 100 to the coating solution may be accomplished within a timeframe of from about 30 seconds to about 1 minute, or longer if desired.

After exposure of the conductive element 100 to the coat-formingcomposition, either by way of direct exposure to the coat-formingcomposition or to a coating solution including the coat-formingcomposition, the coat-forming composition may be cured. The curingconditions may depend on the material used as the coat-formingcomposition. By way of example, the coating material may be cured atabout 125° C. for about one hour to form the coating 170, providing apassivated conductive element 102.

Curing the coat-forming composition may encourage reaction and bondingbetween the coat-forming composition and metallic materials of theconductive element 100, and, depending on the formulation of thecoat-forming composition, nonmetallic materials of the conductiveelement 100. Accordingly, in embodiments in which the coat-formingcomposition includes a functional silane material formulated to reactwith metallic and nonmetallic materials, the coat-forming compositionmay be cured to react the functional silane material with each of theconductive material 112, the barrier material 114, the solder 130, andthe substrate passivation material 126. In such embodiments, forexample, curing may encourage reaction and bonding between thefunctional groups of the functional silane material and each of theconductive material 112, barrier material 114, solder 130, and substratepassivation material 126 to form the coating 170 on and bonded to eachof these materials.

In other embodiments, such as those in which the coat-formingcomposition includes a non-functional silane material, curing mayencourage reaction and bonding between the non-functional silanematerial and each of the conductive material 112, barrier material 114,and solder 130, but not with the substrate passivation material 126.Nonetheless, the coating 170 may continue to be disposed over thesubstrate passivation material 126, though the coating 170 may not bebonded to the substrate passivation material 126.

In still other embodiments, such as those in which the coating 170 isnot bonded to the substrate passivation material 126 or othernonmetallic material(s) of the conductive element 100 (if such othernonmetallic material or materials are present), the coating 170 may betreated to remove the non-bonded regions of the coating to produce acoating 170 over only the components to which the coating 170 is bonded,e.g., the metallic components of the conductive element 100.

It is contemplated that the coating 170 may coat essentially allmaterials otherwise exposed and supported by the substrate 120. Inembodiments in which a functional silane material is used to form thecoating 170, the coating may conformally overlie and be bonded to theelectrically conductive pillar 110, the solder 130, and the substratepassivation material 126. In embodiments in which a non-functionalsilane material is used to form the coating 170, the coating 170 mayconformally overlie and be bonded to the electrically conductive pillar110 and the solder 130 and may also conformally overlie the substratepassivation material 126 but not be bonded to the substrate passivationmaterial 126. Accordingly, in either case, the passivated conductiveelement 102, illustrated in FIG. 1B, is formed.

The semiconductor substrate 120 bearing the passivated conductiveelement 102 may then be further processed as illustrated in FIG. 1C. Forexample, the semiconductor substrate 120 may be inverted and supportedby a conventional carrier material 180 or carrier materials 180 toaccommodate further processing. The carrier material 180 or carriermaterials 180 may include, for example and without limitation, aspin-coated thermoplastic, a spin-coated silicone, a polyimide, asilicone elastomer, a hydrocarbon thermoplastic, a cyclo-olefin, ahigh-temperature adhesive, or a combination thereof. The furtherprocessing may include thinning of the semiconductor substrate 120 byback-grinding or other process. This processing and thinning forms thesemiconductor substrate 120 into what is referred to in the art as a“thinned” wafer. The thinned wafer may then be singulated into a numberof semiconductor dice 150, each die 150 bearing a number of passivatedconductive elements 102 on a major surface thereof. The previouslyreferenced electrically conductive via 122, if present, extends throughthe thickness of the die 150 singulated from the thinned wafer. A die150 may be brought into proximity with another die or other substrate151, illustrated in FIG. 1D. The another die or other substrate 151 maysupport landing pads 140 with which the coated electrically conductivepillars 110 of the passivated conductive elements 102 of die 150 may bealigned for die attach.

During die attach, without removing any material from the coating 170,the solder 130 may be reflowed in proximity to the landing pad 140 ofthe another die or other substrate 151 to electrically and physicallyconnect the electrically conductive pillar 110 of the die 150 with theconductive material of the landing pad 140 of the another die or othersubstrate 151. Flux may optionally be used for the solder 130 reflowwithout deteriorating the bonded coating 170. Alternatively, flux maynot be used during the solder 130 reflow.

The solder 130 may be reflowed by heating the solder 130 above itsmelting point, and such heating may also beneficially deteriorate thecoating 170 in the vicinity of the melted solder 130 proximate to thelanding pad 140, enabling the solder 130 to contact the landing pad 140at, for example, interface region 132. Accordingly, the electricallyconductive pillar 110 of the die 150 becomes electrically and physicallyconnected, also referred to herein as “soldered,” with the landing pad140 of the another die or other substrate 151, while the other materialsof the conductive element 100 remain covered by the coating 170.

Alternatively, the solder 130 may be reflowed by heating the solder 130above its melting point while the coated electrically conductive pillar110 is brought into forced contact with the landing pad 140. Themechanical force, in addition to the heat, may break the coating 170over the solder 130 in the vicinity of the landing pad 140, i.e., atinterface region 132. Thus, as in the case of employing heat to breakdown the coating 170 over solder 130, the electrically conductive pillar110 may be soldered to the landing pad 140 without first removingmaterial from the coating 170 to expose the solder 130. In otherembodiments, the electrically conductive pillar 110 may be soldered tothe landing pad 140 after first removing material from the coating 170to expose at least a portion of the solder 130.

During and after die attach, including solder reflow, the coating 170may remain in place over the substrate passivation material 126, theconductive material 112, and the peripheral edges of barrier material114. As illustrated in FIG. 1D, the coating 170 may also remain over aportion of the solder 130.

The coating 170 isolates at least the conductive material 112 from thesolder 130 to prevent contact between the solder 130 and the coatedcomponents. Since the coating 170 is formed around the electricallyconductive pillar 110, the solder 130 may be inhibited from wicking orslumping along the side of electrically conductive pillar 110,preventing the formation of intermetallic materials caused by thereaction of the solder 130 with the conductive material 112. Also, sincethe coating 170 may be formed from silane, the coating 170 may behydrophobic and non-wettable, which may further inhibit the solder 130from wicking or slumping along the coating 170. In some embodiments,even if the solder 130 should nonetheless flow along the electricallyconductive pillar 110, the solder 130 may flow along the exteriorsurface of the coating 170, rather than between the coating 170 and theconductive materials within the electrically conductive pillar 110(e.g., the conductive material 112 and the barrier material 114),inhibiting contact between the solder 130 and metallic materials of thepassivated conductive element 102 (FIG. 1B).

Because the coating 170 may be chemically bonded to the materials of theelectrically conductive pillar 110, unintentional separation between thecoating 170 and, for example, the conductive material 112 of theelectrically conductive pillar 110, may also be inhibited.

Still further, because the solder 130 may be reflowed and bonded to thelanding pad 140 without prior removal of material from the coating 170,a processing step of exposing the solder 130 prior to solder reflow anddie attach may be avoided.

During die attach, a dielectric underfill material 160 (FIG. 1D) may beadded between the die 150 and the another die or other substrate 151.Coating 170 may enhance adhesion between the underfill material 160 andthe coated materials of the resulting bonded semiconductor die assembly190. As used herein, “underfill material” means and includesconventional between-die filler materials, including nonconductivepaste, which underfill materials may provide mechanical support to theformed semiconductor die assembly 190. The underfill material 160 mayinclude a silane coupling agent, e.g., a silane material including epoxygroups, amine groups, sulfur groups, or any combination thereof. Thesilane material of the underfill material 160 may not chemically reactor bond with the components of the passivated conductive element 102(FIG. 1B), however, not only because the materials will already bepassivated by the coating 170, but because the underfill material 160may not be introduced to the semiconductor die assembly 190 atconditions conducive for reaction between the silane material of theunderfill material 160 and the materials of the passivated conductiveelement 102.

The similarity between a silane material in the underfill material 160and the bonded silane material forming the coating 170 provides enhancedadhesion between the coating 170 and the underfill material 160. Theresulting semiconductor die assembly 190 includes the coating 170 overthe substrate passivation material 126, the conductive material 112, thebarrier material 114, and at least partially over the solder 130 withenhanced adhesion between the underfill material 160 and the coatedmaterials.

After die attach, another die, like die 150 of FIG. 1C, supportinganother passivated conductive element, like passivated conductiveelement 102 of FIG. 1B, may be brought into proximity with anotherlanding pad 142 on another side (e.g., a backside, if the conductiveelement 100 is supported by the active surface) of die 150. The anotherlanding pad 142 may have been formed on die 150, in communication withthe electrically conductive via 122 of die 150, during processing (e.g.,backside processing) of die 150 before die attach. Accordingly,additional semiconductor dice 150 may be stacked and mutually attached,and additional underfill material 160 may be added therebetween, to forma stacked semiconductor die assembly comprising any suitable number ofsemiconductor dice.

With reference to FIGS. 2A through 2D, a conductive element 200 employedin a configuration referred to herein as a “pillar-on-pad” configurationmay likewise be passivated according to the present disclosure. Thepillar-on-pad configuration of the conductive element 200 is like theconductive element 100 of FIG. 1A with the exception that no substratepassivation material 126 (FIG. 1A) is disposed over the bond pad 124.The electrically conductive pillar 110 is supported entirely on the bondpad 124 and may be of the same lateral dimension as bond pad 124, asshown. Alternatively, the bond pad 124 may extend laterally beyond theelectrically conductive pillar 110. With such configurations, extremewicking or slumping of solder 130 before, during, or after die attachcould bring the slumping or wicking solder into contact with theconductive material of the bond pad 124 and cause formation ofintermetallic materials in or around the bond pad 124, corrosion of thebond pad 124, or other damage to the bond pad 124. However, inaccordance with the present disclosure, a coating 270 may be formed overand be bonded to the otherwise-exposed surface(s) of the bond pad 124 toisolate and protect the bond pad 124 from contact with the solder 130 ofthe conductive element 200, as illustrated in FIG. 2B.

The coating 270 may be formed as described above with regard to FIG. 1B.However, in forming the coating 270, exposing the conductive element 200to the coat-forming composition (e.g., the coat-forming compositionwithin the coating solution) includes exposing a surface of thesubstrate 120, e.g., an active surface of the substrate 120, and asurface or surfaces of the bond pad 124 to the coating material as wellas exposing surfaces of the conductive material 112, the barriermaterial 114, and the solder 130 to the coating material.

The coat-forming composition may be formulated to react with themetallic material of the bond pad 124 such that the resulting coating270 is bonded to the otherwise-exposed surface of the bond pad 124. Thebond pad 124 may include hydroxyl groups on its sidewalls due toexposure of the sidewalls to oxygen, to water, or to both, whichhydroxyl groups may react with and bond to silanol or other functionalgroups within a non-functional or functional silane material within thecoat-forming composition to form the coating 270 on the surfaces of thebond pad 124.

Alternatively or additionally, the coat-forming composition may beformulated to react with the material of the substrate 120, e.g.,silicon within the substrate 120. Such a coat-forming composition may beformulated to react with silicon oxides, e.g., native oxide, on theexposed surface of the substrate 120. For example, and withoutlimitation, the coat-forming composition may include a silane materialthat has been hydrolyzed to form silanol groups reactive with silicon ofthe substrate 120.

Accordingly, the coating 270 may be formed over essentially allotherwise-exposed surfaces of the components of the conductive element200. The resulting, passivated conductive element 202 may then beinverted, supported by one or more conventional carrier materials 180,as illustrated in FIG. 2C, and further processed, e.g., thinned, toprepare a thinned wafer, and then singulated to prepare semiconductordice 150, each bearing a number of passivated conductive elements 202 ona major surface thereof. As described with regard to FIG. 1D, die 150may be aligned with another die or other substrate 151, and the solder130 reflowed to attach the die 150 to the another die or other substrate151, forming a bonded conductive element, i.e., semiconductor dieassembly 290. To accomplish the die attach, material may not be removedfrom the coating 270 before solder reflow and bonding. Rather, heatingthe solder 130 may also beneficially deteriorate the coating 270 in thevicinity of the landing pad 140 to allow direct, physical contactbetween the reflowed solder 130 and the landing pad 140 at, for example,interface region 132.

In other embodiments, die attach may include mechanically-forced contactbetween the passivated conductive element 202 and the landing pad 140 ofthe another die or substrate 151, e.g., die attach by thermalcompression bonding. The mechanical force may thin or break the coating270 in the vicinity of the landing pad 140 to allow contact between thesolder 130 of die 150 and the landing pad 140 of the another die orother substrate 151. Accordingly, a processing step of removing materialfrom the coating 270, such as to expose a surface of the solder 130before the die attach, may be avoided.

Again, an underfill material 160 may be included between the die 150 andthe another die or other substrate 151, and the coating 270 mayencourage adhesion between the electrically conductive pillar 110 andthe underfill material 160. In some embodiments, the underfill material160 may be included between the die 150 and the another die or othersubstrate 151 before reflow of the solder 130. Further, because thecoating 270 isolates the solder 130 from the conductive material 112 andfrom the bond pad 124, the coating 270 may also inhibit deterioration ofthe electrically conductive pillar 110 and deterioration of the bond pad124 without use of a substrate passivation material 126 (e.g., FIGS. 1Athrough 1D). The coating 270 may also inhibit wicking or slumping of thesolder 130 because the coating 270 remains at least partially over sidesof the solder 130, even after die attach. Even should the solder 130slump or wick, the coating 270 remaining over the sidewalls of theconductive material 112, the barrier material 114, and the bond pad 124inhibits contact between the wicking or slumping solder and the coatedcomponents.

Another embodiment of the present disclosure is illustrated in FIGS. 3Athrough 3D. The illustrated pillar-on-passivation conductive element 100may be selectively coated with a coating material selective for theconductive material 112 of the electrically conductive pillar 110, asillustrated in FIG. 3B. In embodiments in which the conductive material112 includes or consists essentially of copper, either on the outersurface of the conductive material 112 or throughout the conductivematerial 112, the coating material may be selective for copper. Theselective coating material forms a selective coating 370 overessentially only sidewalls of one or more, but not all, components ofthe conductive element 100. For example, without limitation, theselective coating material may be formulated to form the selectivecoating 370 on only the conductive material 112.

For example, and without limitation, the selective coating material mayinclude an organic solderability protectant (or preservative) material,generally known in the art as an “OSP.” The OSP may include, for exampleand without limitation, a benzotriazole, an imidazole, or a combinationthereof. The OSP may be selective for the metal of the conductivematerial 112 and be formulated to inhibit oxidation of the conductivematerial 112 on which the selective coating 370 is formed. The OSP mayalso be formulated to be resistant to high temperatures, e.g.,formulated to withstand temperatures up to about 250° C., e.g., 220° C.,without deteriorating.

Some conventional OSPs are vulnerable to deterioration in the presenceof conventional flux materials. Accordingly, flux may or may not be usedduring die attach following formation of the selective coating 370depending on the OSP chosen. However, some conventional OSPs areformulated to be less vulnerable to flux materials, such that flux maybe used during die attach. In either regard, flux may be used during aninitial reflow of the solder 130, prior to formation of the selectivecoating 370, such as to achieve the solder 130 of a rounded shape, asillustrated in FIG. 3A.

The passivated conductive element 302 may then be processed, asillustrated in FIG. 3C. During processing and subsequent die attach, asillustrated in FIG. 3D, the selective coating 370 isolates theconductive material 112 from the solder 130. Therefore, if the solder130 should slump or begin to wick along the electrically conductivepillar 110, the selective coating 370 inhibits the solder 130 fromcoming into contact with the conductive material 112 of the bondedconductive element, i.e., semiconductor die assembly 390. Further,because the selective coating 370 forms substantially only on theconductive material 112, removing material from the selective coating370 to expose a portion of the solder 130 before soldering theelectrically conductive pillar 110 to the landing pad 140 may beavoided. The resulting bonded conductive element, i.e., semiconductordie assembly 390, includes the selective coating 370 along the sidewallsof the conductive material 112. The selective coating 370 may enhanceadhesion with the underfill material 160.

As illustrated in FIGS. 4A through 4D, a selective coating 470 may alsobe used with a conductive element 200 of a pillar-on-pad configuration.As illustrated in FIG. 4B, because the selective coating 470 isselective for the conductive material 112, the selective coating 470 isformed essentially only on sidewalls of the conductive material 112,leaving the passivated conductive element 402 with the sidewalls of thebond pad 124 and the surface of the substrate 120 exposed in addition tothe sidewalls of the barrier material 114 and the surface of the solder130. The passivated conductive element 402 may thereafter be processed,as illustrated in FIG. 4C, and attached to the first die 151, asillustrated in FIG. 4D. Again, because the selective coating 470 formsessentially only on the conductive material 112, removing material fromthe selective coating 470 to expose the solder 130 to the landing pad140 may be avoided. The resulting bonded conductive element, i.e.,semiconductor die assembly 490, includes the selective coating 470 alongthe sidewalls of the conductive material 112.

Another embodiment is illustrated in FIGS. 5A through 5D. As illustratedin FIG. 5A, the electrically conductive pillar 110 of a conductiveelement 500 may not initially support a solder mass, unlike theelectrically conductive pillars 110 of FIGS. 1A, 2A, 3A, and 4A. (ThoughFIG. 5A illustrates the electrically conductive pillar 110 in apillar-on-passivation configuration, the electrically conductive pillar110 may alternatively be in a pillar-on-pad configuration.) Theelectrically conductive pillar 110 may be coated with a coating 570formed from a coating material, e.g., a silane-including coatingmaterial, as described above with regard to FIGS. 1A through 2D. Inembodiments in which the coating material includes a silane material,either non-functional or functional, the coating 570 may be formed overthe conductive material 112 and barrier material 114. Inpillar-on-passivation configuration embodiments in which the coatingmaterial includes a silane material that is functional, the coating 570may also be formed over the substrate passivation material 126, asillustrated in FIG. 5B. In pillar-on-pad configurations (e.g., like thatof FIG. 2B) in which the coating material includes a silane materialthat is functional, the coating may formed over the otherwise-exposedsurface(s) of the bond pad 124 and the substrate 120 as well as on othermetallic materials of the electrically conductive pillar 110.

The resulting passivated conductive element 502, illustrated in FIG. 5B,may then be inverted and brought into proximity with a solder ball 530made up of the solder 130, as illustrated in FIG. 5C, supported by alanding pad 140 on another die or other substrate 151. Reflowing thesolder 130 of the solder ball 530 in proximity with the electricallyconductive pillar 110, either with force or without force, may breakdown the coating 570 disposed between the barrier material 114 and thesolder 130 to bring the barrier material 114 and solder 130 intophysical contact with one another so as to solder the electricallyconductive pillar 110 to the landing pad 140. Alternatively, heating thesolder 130 to reflow the solder 130 may also heat and deteriorate thecoating 570 where it is in contact with solder 130, such that thesection of the coating 570 breaks down and allows bonding of theelectrically conductive pillar 110 to the landing pad 140. Removingmaterial from the coating 570 prior to solder reflow may be avoided. Inother embodiments, however, material may be removed from the coating 570prior to solder reflow to expose at least a portion of the electricallyconductive pillar 110 to the solder 130 of the solder ball 530.

As illustrated in FIG. 5D, the resulting bonded conductive element,i.e., semiconductor die assembly 590, includes the coating 570 on eachof the barrier material 114, conductive material 112, and substratepassivation material 126, but not substantially on the solder 130. Inembodiments in which the conductive element 500 was of a pillar-on-padconfiguration (like that of FIG. 2D), the resulting bonded conductiveelement (not shown) may include the coating on each of the barriermaterial 114, the conductive material 112, the bond pad 124, and thesubstrate 120 (e.g., a front side of die 150, as in the embodiment ofFIG. 2D).

Further, though not shown, a selective coating, like the selectivecoating 370 of FIGS. 3B through 3D or the selective coating 470 of FIGS.4B through 4D, may alternatively be formed as described above withregard to FIGS. 3B through 3D or FIGS. 4B through 4D, on a conductiveelement 500 of either the illustrated pillar-on-passivationconfiguration or a pillar-on-pad configuration. The resulting bonded dieassembly would include a coating on essentially only the conductivematerial 112.

Though FIGS. 1A through 5D illustrate only a single electricallyconductive pillar 110, it is contemplated, as noted above, that inpractice one die 150 supports a plurality, even hundreds, ofelectrically conductive pillars 110 and that multiple dice 150 may bestacked to form a stacked semiconductor die assembly, as illustrated inFIGS. 6 through 10. Therefore, an additional semiconductor die 152,supporting a plurality of passivated conductive elements (e.g.,passivated conductive elements 102, 202, 302, 402, 502) may be stackedatop the die 150, as illustrated in FIGS. 6 through 10. Likewise, afourth, fifth, or so on die may be so stacked.

FIG. 6 illustrates such a stacked array 600 comprising a plurality ofbonded conductive elements, i.e., semiconductor die assemblies 190,which may have been formed in accordance with the method illustrated inFIGS. 1A through 1D.

FIG. 7 illustrates a stacked array 700 comprising a plurality of bondedconductive elements, i.e., semiconductor die assemblies 290, which mayhave been formed in accordance with the method illustrated in FIGS. 2Athrough 2D.

FIG. 8 illustrates a stacked array 800 comprising a plurality of bondedconductive elements, i.e., semiconductor die assemblies 390, which mayhave been formed in accordance with the method illustrated in FIGS. 3Athrough 3D.

FIG. 9 illustrates a stacked array 900 comprising a plurality of bondedconductive elements, i.e., semiconductor die assemblies 490, which mayhave been formed in accordance with the method illustrated in FIGS. 4Athrough 4D.

FIG. 10 illustrates a stacked array 1000 comprising a plurality ofbonded conductive elements, i.e., semiconductor die assemblies 590,which may have been formed in accordance with the method illustrated inFIGS. 5A through 5D.

Alternatively, in embodiments in which the coating is applied prior tosolder reflow for die attach, the bonded conductive element may be againexposed to the coating material after solder reflow and die attach, butbefore inclusion of the underfill material 160. This second exposure tothe coating material (e.g., to the coating material within a coatingsolution) may re-coat any surfaces of the bonded conductive elementsthat became exposed, i.e., uncoated, during processing between theinitial coating formation and completion of the die attach. In suchembodiments, the resulting bonded conductive element, following secondor subsequent exposure to the coating material, may further include thecoating over otherwise-exposed surfaces of the landing pad 140 and thenon-active surface, e.g., backside, of the another die or othersubstrate 151. Therefore, the coating may also enhance adhesion betweenthe subsequently-included underfill material 160 and the landing pad 140and the another die or other substrate 151.

As described above, disclosed is a method of forming a semiconductor dieassembly, comprising forming a coating on an electrically conductivepillar, comprising exposing at least a portion of the electricallyconductive pillar to at least one of a silane material and an organicsolderability protectant material. Solder is reflowed between theelectrically conductive pillar and a landing pad to electrically andphysically connect the electrically conductive pillar to the landing padwithout removing material from the coating.

Also disclosed is a method of forming a semiconductor die assembly,comprising forming a coating on solder of an electrically conductivepillar. The coating is formed from at least one of a silane material andan organic solderability protectant material. Without removing materialfrom the coating, a conductive material of the electrically conductivepillar is attached to a landing pad by reflowing the solder.

Still further is disclosed a semiconductor assembly, comprising aconductive element on a semiconductor substrate. Solder electricallyconnects the conductive element to a landing pad of another substrate.The semiconductor assembly also comprises a coating on the conductiveelement and at least partially on the solder. The coating comprises atleast one of metal-oxygen-silicon bonds, silicon-oxygen-silicon bonds,metal-sulfur bonds and silicon bonds, and an organic solderabilityprotectant material.

Additionally, disclosed is a structure, comprising a conductive materialdisposed over a substrate and supporting a solder mass. A coating isbonded to the conductive material and isolates an exterior surface ofthe conductive material from the solder mass. The coating comprises atleast one of an organic solderability protectant material and siliconbonded to oxygen.

Moreover, disclosed is a structure, comprising a conductive materialdisposed over a substrate. A coating is bonded to the conductivematerial. The coating comprises at least one of an organic solderabilityprotectant material and silicon-to-oxygen bonds.

While the disclosed device structures and methods are susceptible tovarious modifications and alternative forms in implementation thereof,specific embodiments have been shown by way of example in the drawingsand have been described in detail herein. However, it should beunderstood that the present disclosure is not intended to be limited tothe particular forms disclosed. Rather, the present inventionencompasses all modifications, combinations, equivalents, variations,and alternatives falling within the scope of the following appendedclaims and their legal equivalents.

What is claimed is:
 1. A semiconductor assembly, comprising: aconductive element on a semiconductor substrate; solder electricallyconnecting the conductive element to a landing pad of another substrate;and a coating on the conductive element and substantially conforming toand fully covering an at least partially rounded exterior surface of thesolder, the coating comprising at least one of metal-oxygen-siliconbonds, silicon-oxygen-silicon bonds, metal-sulfur bonds and siliconbonds, and an organic solderability protectant material.
 2. Thesemiconductor assembly of claim 1, wherein the coating alsosubstantially conforms to the conductive element.
 3. The semiconductorassembly of claim 1, wherein the conductive element contacts a bond pad,and the coating is further on the bond pad.
 4. The semiconductorassembly of claim 3, wherein the coating fully covers sidewalls of thebond pad.
 5. The semiconductor assembly of claim 1, wherein the coatingis bonded to the solder.
 6. The semiconductor assembly of claim 1,wherein the coating is formed from a silane material.
 7. A structure,comprising: a conductive material disposed over a substrate andsupporting a solder mass; a barrier material disposed between theconductive material and the solder mass: and a coating bonded to theconductive material and to the barrier material and isolating anexterior surface of the conductive material and an exterior surface ofthe barrier material from the solder mass, the coating substantiallyconforming to and extending along a rounded exterior surface of thesolder mass from the barrier material to a landing pad, the coatingcomprising at least one of: an organic solderability protectantmaterial, and silicon bonded to oxygen.
 8. The structure of claim 7,wherein the coating is bonded to the conductive material, the barriermaterial, and the solder mass.
 9. The structure of claim 7, wherein thecoating is bonded to the conductive material by at least one ofmetal-oxygen-silicon bonds and metal-sulfur bonds.
 10. The structure ofclaim 7, wherein the coating comprises the silicon bonded to oxygen. 11.The structure of claim 10, wherein the coating is formed from a silanematerial.
 12. The structure of claim 7, further comprising a substratepassivation material at least partially overlying a bond pad on thesubstrate, wherein the coating is at least partially disposed on thesubstrate passivation material.
 13. A structure, comprising: aconductive material disposed directly on a bond pad over a semiconductorsubstrate without a passivation material on the bond pad; a coatingbonded to the conductive material and substantially conforming to arounded surface of a solder mass overlying the conductive material, thecoating comprising at least one of an organic solderability protectantmaterial and silicon-to-oxygen bonds; and a dielectric underfillmaterial on the coating, at least one of the coating and the dielectricunderfill material in physical contact with the semiconductor substrate.14. The structure of claim 13, further comprising: a barrier materialdisposed over an end of the conductive material, wherein the coating isbonded to the conductive material and the barrier material.
 15. Thestructure of claim 13, wherein the coating is bonded to the conductivematerial by at least one of metal-oxygen-silicon bonds and metal-sulfurbonds.
 16. The structure of claim 13, wherein the coating is also bondedto the bond pad.